408 University of California Publications in Zoology [Vol. in 



lip, i.e., the dorsal lip strand; (2) that a fine strand, the ventral motor 

 strand, ran from it to the bases of the adoral membranelles, also that 

 a branch strand left this ventral motor strand and passed along the 

 base of the inner adoral lip, the adoral lip strand, and that many well- 

 defined fibers passed from it, following the contour of the operculum 

 toward the right to become lost in the immediate vicinity of the base 

 of the right skeletal structure. These are the opercular fibers. Most 

 interesting of all. however, was the apparently perfectly definite con- 

 nection with a ring of the substance surrounding the oesophagus at 

 just about the level of the outer adoral furrow. This ring, which is 

 designated as the circumoesophageal. as well as all of the fibers 

 described as leaving the motorium, showed in all regions the same 

 bright red color. Other fibers also staining bright red are found in the 

 oesophageal walls. These are found in the oesophageal walls. These 

 are called the oesophageal fibers, but thus far it has not been definitely 

 decided whether they take their origin from the motorium or directly 

 from the circumoesophageal ring, probably the latter, however" 

 (Sharp, 1914, p. 83). 



Inasmuch as this complex system of motor mass and strands is 

 intimately associated with the motor organelles, one is justified here, 

 as in the case of the flagellates, in regarding these structures as a part 

 of the animal's motor mechanism, whatever their specific role may be. 

 But just what is their specific function? Three possibilities were 

 obvious: (1) this intracytoplasmic system may be skeletal, for sup- 

 port; (2) it may be muscular, the strands representing primitive con- 

 tractile fibrils; or (3) these strands may have conductive properties 

 with the motorium functioning as a coordinating center for impulses 

 passing over the primitive neural fibrils. After weighing the evidence 

 which his investigations had disclosed, Sharp concluded that the last 

 hypothesis was in nearest agreement with the facts. 



The skeletal hypothesis, adopted by Braune (1913) for a similar 

 system found in Ophryoscolex purkynjei of the same family as Diplo- 

 iliiiiiin) ecaudatum, was believed by Sharp to be insufficient for his 

 species. The diminutive size of the "motor mass," its nonconformity 

 in shape to the particular region of its location, and the want of 

 attachment of the several strands to any fixed structures were con- 

 ditions unfavorable to such an interpretation. 



Nor did it seem probable that the mechanism is contractile in 

 function. If it were so, it should appear attached to fixed structures, 

 on the one hand, in order to affect movable structures, on the other, 



